Rise of Humanity

Seeing why many friends can quickly understand why they are carrying heavy stones in Chapter 21, and even ridicule the common sense of house pigs, house pigs need to explain.

Many people know that Galileo's Leaning Tower test. One large, one small, and two iron **** fell from the Leaning Tower at the same time and fell to the ground at the same time. Some people said that it was in elementary school textbooks. Air buoyancy.

Air buoyancy is small, but it also affects larger objects. In addition, the biggest impact on the acceleration of gravity is air resistance and wind resistance.

When a person falls from a high altitude, the wind resistance will offset the acceleration and allow the fall speed to reach a fixed value. The fixed value is 25 meters to 50 meters per second, which cannot exceed this speed.

石头 The density of the stone is seven times that of the human body, the potential energy is greater, and the effect of wind resistance is smaller, so the speed can be faster.

So, is Galileo's Leaning Tower test correct? Who is faster if two iron balls, one large and one small, fall at the same height?

Let's use junior high school physics to calculate.

Two round stones, one large and one small, have air resistance Fw = 1/16 · A · Cw · v ^ 2. Set CW = 1, A1 = 1, A2 = r ^ 2, mass m1 = 1, m = r ^ 3. r> 1 then air resistance FW1 = 1/16 * V1 ^ 2FW2 = 1/16 * V2 ^ 2 * r ^ 2

Gravity: G1 = g, G2 = r ^ 3 * g

1. If the speed is the same, the acceleration a1 = (g－1 / 16 * v ^ 2), a2 = (r ^ 3 * g－1 / 16 * v ^ 2 * r ^ 2) / r ^ 3 = ( g－1 / 16 * v ^ 2 * 1 / r)> a1a2> a1, the acceleration of large stones is fast.

2, when the limit speed is reached, the speed does not increase. Then 1/16 * v1 ^ 2 = g, 1/16 * v2 ^ 2 * r ^ 2 = r ^ 3 * g, 1/16 * v2 ^ 2 = r * g, V2> V1, the large iron ball moves at a constant speed The final speed is large. So the big iron ball landed first.

3. It is more difficult to calculate in the case of calculating air buoyancy, but there is a simple method to test it in water. Water also has buoyancy. Take an iron ball and a piece of meat and fall into the water to see who falls first. Obviously the iron ball landed first.

A similar test can be used for a tadpole, that is, an ant and an ant lying on a rock fall from the air at the same height at the same time.

还有 If you still have questions about this, go to junior high school physics and calculate more. Don't take it for granted. ;

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